Numerous systems have been devised over the years in order to assist medical personnel in delivering and positioning medical implants, for example, prosthetic occluders, within the human body, preferably, in a minimally invasive manner. One of the concerns of the implant delivery systems currently on the market is premature release at an undesired site in the patient's body during delivery of the implant. If an implant is released before it arrives at the intended location, not only is the intended purpose not achieved, the implant may also pose a danger to the patient at the undesired location until the implant is repositioned or removed.
Another problem with many of the known delivery systems is that they can often adversely affect proper positioning of the device that is being implanted, which forces the doctor to estimate and take into consideration such effect when assessing the final implant position prior to releasing the implant. For example, most of the delivery systems include an elongated catheter that is used to access various passageways inside a patient's body. Often the desired position of the implant may not align with the longitudinal axis of the catheter. If the juncture between the implant and the catheter lacks sufficient flexibility, tension will be generated at the juncture when the implant has to be bent off the catheter's axis in order to assume the desire position. Upon release of the implant, the tension will affect both the implant and the delivery catheter, causing shifting in the implant position, and possible trauma to the surrounding tissue as the distal end of the catheter springs back to a more relaxed state. Such shifting in the implant position may result in a less desirable medical result (such as a residual leak in the case of septal occluders). Further, because of the possibility of trauma to surrounding tissues and organs, later device embolization may occur.
Implants may include devices designed for compression into a small size tube or catheter to facilitate their introduction into the vasculature of the patient. The implants are subsequently expandable either to occlude defects or holes in the heart, in the case of septal occluders, or to contact the walls of the passageway (e.g., blood vessels), in the case of vena cava filters or stents. Among these devices are septal occluders well-known in the art such as the occluder described in U.S. Pat. No. 5,425,744 issued to Fagan et al. Septal occluders are useful in treating medical conditions such as patent foramen ovale (PFO), which is a persistent, one-way, often flap-like opening in the wall between the right atrium and left atrium of the heart, as well as other congenital and acquired defects in the heart or vasculature.
Presently, ball-to-ball (or pin-to-pin) attach/release mechanisms, such as the attach/release mechanism illustrated in Transcatheter Therapy in Pediatric Cardiology (1993): 335-348, have been employed by one skilled in the art to implant and position such septal occluders within the heart. The pin-to-pin mechanism illustrates the adverse effect the attachment juncture may cause in the positioning of the implant. With pin-to-pin mechanisms, the implant, a septal occluder, for example, is held nearly perpendicular to the longitudinal axis of a sleeve on the distal end of the delivery catheter. Due to the acute angle of delivery of the septal occluder from the inferior vena cava to the septal wall, the rigid pin-to-pin connection applies tension to the implant and the underlying septum, and compromises precise assessment of the final implant position upon release of the implant.
Other types of attachment mechanisms known in the art include threaded male and female members as described in U.S. Pat. No. 5,725,552 issued to Kotula et al. This system, however, requires axial rotation of the members with respect to each other to disconnect the delivery device and also provides little flexibility, if any, for the lateral pivoting of the implant at the point it is attached to the delivery device.
Accordingly, there is a need for an interventional delivery system that prevents premature release of the attached implant, provides precise positioning of the implant, and also allows recapture of the implant.